Daniel Acker/Bloomberg via Getty Images(NEW YORK) -- Retailers ring up as much as 40 percent of the entire year's sales between Black Friday and Christmas day. But there is one segment of stores that skips the holiday hoopla: Dollar stores. In fact, they seem to fly under the retail radar all year long.

The three top players -- Family Dollar, Dollar Tree and Dollar General -- have quietly become a $56 billion industry and they are opening new locations faster than Starbucks. By one estimate, there are more dollar stores in the United States than drug stores.

"Believe it or not, we can still open a lot of stores," said Family Dollar CEO Howard Levine. "Particularly in California where we just opened a store a year ago… this is probably a 1,000-store state."

Right now, Levine overseas an empire of 7,550 stores nationwide -- and counting. Family Dollar opened 500 new stores this year -- more than one per day.

"If somebody told me I was cheap, I would take that as a compliment," he said. "That means we are looking for value. That means we don't overpay for stuff."

When asked what his answer was to the stereotype that dollar stores only sell junk, Levine said, "I say you haven't been in a Family Dollar, maybe ever, to make that kind of comment."

But cheap is working. The three dollar chains are Fortune 500 companies.

Another chain, 99 Cents Only, is eyeing real estate on Beverly Hill's ritzy Rodeo Drive. There is already a store on Wilshire Boulevard -- not far away -- and it is the chain's best-performing location. It makes double the sales of most others.

Dollar stores have been expanding while the rest of the economy has been receding. Family Dollar has been doing well more than a half century. Levine's father opened the first one in Charlotte, N.C., in 1959.

"My friends say, 'I'm miserable, but you must love this economy,'" Levine said. "That's not really the case. We would much prefer a strong economy, strong employment. People need jobs and when people have jobs, they spend money. We do pretty well in a tough time, but we do very well in good times."

In the beginning, Family Dollar sold only things that cost a buck, but they abandoned that years ago. Today, roughly 90 percent of their products are less than $10. About one-third of everything they sell is not made in America, but Levine said that's just the nature of the business.

"Unfortunately, a lot of manufacturing has gone overseas," he said. "They have a cheap way of doing it and consumers accept it. There is no backlash from that so you got to go where you get the value and you got to go where you have the workmanship and the factories to do that."